JP2009018628A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device which is capable of separating a gear housing and a motor housing from each other, and positioning a worm in the axial direction, and simplified. <P>SOLUTION: A motor housing 20 having a deceleration mechanism which consists of a worm 31 and a worm wheel 29 and decelerates and transmits the power from an electric motor 19, and two bearings 35, 37 for pivotably supporting the worm 31 by both shaft ends with the electric motor being mounted thereon, and a gear housing 9 with the deceleration mechanism being mounted thereon are separably coupled with each other. A coupling structure of the motor housing 20 with the gear housing 9 is constituted so that the worm 31 is positioned in the axial direction when coupling both housings. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering device for a vehicle.

  In the electric power steering device, an auxiliary steering torque is generated from the electric motor in response to the steering torque applied to the steering wheel, and is decelerated by a power transmission mechanism including a reduction mechanism and transmitted to the output shaft of the steering mechanism. It has become.

  In an electric power steering apparatus using a worm reduction mechanism as the power transmission mechanism, a worm wheel meshes with a worm on the drive shaft side of the electric motor, and this worm wheel is an output shaft (for example, a pinion shaft) of the steering mechanism. And the column shaft). As the electric power steering device, a so-called pinion assist type in which the output shaft of the steering mechanism is a pinion shaft, or a so-called column assist type in which the output shaft of the steering mechanism is a column shaft is known.

In an electric power steering apparatus, a motor housing to which an electric motor is attached and a gear housing to which a speed reduction mechanism is attached are configured in an integrated structure (for example, Patent Document 1), and a motor housing to which an electric motor is attached and a speed reduction mechanism portion are attached. There is a gear housing (for example, Patent Document 2) that is a separate body and is separably coupled to each other. The latter case is suitable for dealing with a change in the vehicle layout in which only the mounting phase of the electric motor such as a sister car or a derivative car is different.
Japanese Patent Application No. 2006-120915 JP-A-11-78916

  However, in a conventional electric power steering device in which a motor housing to which an electric motor is attached and a gear housing that houses a speed reduction mechanism are separated, a snap ring is provided to position and restrain the worm attached to the motor shaft in the axial direction. There has been a demand for further simplification of configuration such as use.

  Therefore, an object of the present invention is to provide an electric power steering device that can be easily assembled by further improving the electric power steering having a configuration in which the gear housing and the motor housing can be separated.

In order to achieve the above object, the present invention has an auxiliary power transmission mechanism including an electric motor, a speed reduction mechanism including a worm coupled to a rotation output shaft of the electric motor and a worm wheel meshing with the worm, In the electric power steering apparatus having a configuration in which the motor housing for the electric motor and the gear housing to which the speed reduction mechanism is attached are detachably coupled,
The worm is supported by the gear housing by two bearings so as to be finely movable in the axial direction and loaded with a preload toward the electric motor side,
Of the two bearings, a bearing closer to the electric motor is supported in the axial direction by the motor housing.

  As described above, according to the present invention, the structure of the motor housing and the gear housing is configured such that the worm is positioned and restrained in the axial direction when they are combined. Therefore, the snap ring used for this purpose becomes unnecessary, and the cost can be reduced and the configuration can be simplified.

  Further, as a preferred aspect of the electric power steering device of the present invention, an elastic member can be disposed on the opposing surface that contacts the side end surface of the bearing on the electric motor side. In this case, the engagement of the engagement between the worm and the worm wheel is achieved. Sound and backlash can be prevented.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an electric power steering apparatus according to a preferred embodiment of the present invention.

  In FIG. 1, an electric power steering apparatus 1 includes a steering column 7 that rotatably supports a steering shaft 5 having a steering wheel 3 attached to a rear end thereof. A gear housing 9 that houses a speed reduction mechanism portion of the electric assist mechanism is connected and fixed to the front end portion of the steering column 7. The speed reduction mechanism is a known mechanism including a worm and a worm wheel meshing with the worm. A cover 11 that extends radially outward of the steering column 7 is fixed to the front end of the gear housing 9.

  The steering column 7 is fixed to the vehicle body side member 15 via the upper bracket 13. The gear housing 9 and the cover 11 are fixed to the vehicle body side member 15 via the lower bracket 17. A motor housing 20 for the electric motor 19 formed separately from the gear housing 9 is attached to the gear housing 9, which will be described in detail later.

  When the vehicle travels, the electric power steering device 1 drives the electric motor 19 according to the steering torque generated by the operation of the steering wheel 3, and the rotational force is transmitted to the output shaft 21 via the speed reduction mechanism. The rotational force transmitted to the output shaft 21 is transmitted to a gear box (not shown) via a lower steering shaft 25 connected to the front end portion of the output shaft 21 via a universal joint 23 in order toward the front of the vehicle. And steer the running wheels.

  The electric power steering apparatus 1 of the present embodiment is capable of tilt adjustment, and a tilt mechanism is configured by the tilt pivot TP at the top of the cover, the lever 27 provided on the upper bracket 13 and the like.

  FIG. 2 is a partial sectional view in the motor axis direction showing the main part of the present embodiment.

  In FIG. 2, a motor housing 20 to which an electric motor 19 is attached and a gear housing 9 to which a speed reduction mechanism is attached are shown. The motor housing 20 is formed integrally with the electric motor 19. A cylindrical portion 20a is integrally formed on the gear housing 9 side of the motor housing 20 so as to project the rotation output shaft 19a of the electric motor 19 with an annular space and project to the gear housing 9 side. A flat end surface 20 b extending from the rotation output shaft 19 a of the electric motor 19 toward the peripheral edge of the motor housing 20 at a right angle is formed.

  On the other hand, the gear housing 9 that houses a speed reduction mechanism including a worm wheel 29 that is externally fitted and fixed to the output shaft 21 and a worm 31 that meshes with the worm wheel 29 is opposed to the motor housing 20 and has a cylindrical portion 9a integrally therewith. The cylindrical portion 9a has an inner peripheral surface to which the cylindrical portion 20a of the motor housing 20 is fitted and joined, and forms a flat end surface 9b to be joined to the flat end surface 20b of the motor housing 20. ing.

  In this way, the gear housing 9 and the motor housing 20 are fitted with the cylindrical portion 9a of the motor housing 9 and the cylindrical portion 20a of the motor housing 20, and are joined at the respective end surface portions 9b and 20b. Both are joined by being fastened. As described above, the gear housing 9 and the motor housing 20 are separate structures and coupled to each other, but are separable as necessary.

  The worm 31 that constitutes the speed reduction mechanism together with the worm wheel 29 is spline-fitted to the rotation output shaft 19a of the electric motor 19, and at both ends thereof, a motor-side bearing 35 on the side close to the electric motor 19, The gear housing 9 is rotatably supported by an anti-motor side bearing 37 on the side away from the electric motor 19.

  The motor-side bearing 35 has an outer periphery fitted into the inner circumferential surface of the gear housing 9 and is fitted onto the outer circumferential portion of the motor-side end portion of the worm 31 to support a radial load. One end of the axial end of the outer ring 35 a of the motor-side bearing 35 contacts the surface of the gear housing 9, and the other contacts the front end surface of the cylindrical portion 20 a of the motor housing 20, whereby the motor-side bearing 35 is connected to the gear housing 9. And the motor housing 20 are supported in the axial direction.

  Both axial sides of the inner ring 35b of the motor-side bearing 35 are compressed between a worm enlarged diameter portion 31a provided at the end of the worm 31 and a nut 38 fixed to the end of the worm end on the motor 19 side. A pair of rubber dampers 39 and 41 are elastically supported in the axial direction. Thus, the worm 31 can be displaced in the axial direction with respect to the motor-side bearing 35 within the elastic limit of the rubber dampers 39 and 41.

  On the non-motor side of the worm 31, a preload mechanism 42 is provided that presses the end portion on the non-motor side of the worm 31 in a direction to bring the worm 31 closer to the worm wheel 29 side to preload.

  The preload mechanism 42 is provided on the bush 43 interposed between the outer peripheral surface of the worm 31 on the non-motor-side diameter-expanded portion 31b and the inner peripheral surface of the counter-motor-side bearing 37, and on the small-diameter tip portion 31c side of the worm 31. The preload pad 45 and a torsion coil spring 46 wound around the outer peripheral surface of the preload pad 45 are configured.

  Accordingly, the small-diameter tip 31c on the counter-motor side of the worm 31 can be elastically urged with a constant load in a direction in which the worm 31 approaches the worm wheel 29, so that the rattling of the mesh can be eliminated. It has become.

  When the motor housing 20 and the gear housing 9 are fitted to the cylindrical portions 20a and 9a, joined at the joining end face portions 20b and 9b, and fastened with the bolts 33, the motor side end face of the motor side bearing 35 is the motor. While being in contact with the end surface of the cylindrical portion 20a of the housing 20, the bearing fitting portion 9c provided on the inner surface side of the cylindrical portion 9a of the gear housing 9 is in contact with the end surface and the outer peripheral surface of the motor side bearing 35 on the worm 31 side. These are positioned and restrained in the axial direction and the radial direction, whereby the worm 31 is positioned in the axial direction.

  Thus, the engagement structure in the vicinity of the joint between the motor housing 20 and the gear housing 9 is configured such that the worm 31 is positioned and restrained in the axial direction when the housings 20 and 9 are coupled. Therefore, the snap ring conventionally used for positioning and restraining the worm 31 is not necessary, and the cost can be reduced.

  FIG. 3 is an enlarged view of a portion A showing an embodiment in which an elastic member is used in the electric power steering device of FIG.

  In the above embodiment, as shown in FIG. 3, an annular groove 20 c is provided on the end surface of the cylindrical portion 20 a of the motor housing 20 that contacts the motor side end surface of the motor side bearing 35, and a ring-shaped elastic member 49 is fitted into this. It can also be a complicated configuration.

  As a result, the worm 31 is slightly urged in the axial direction to apply a preload, so that the hitting sound and rattling of the worm 31 and the worm wheel 29 can be prevented.

  4 is an enlarged view of a portion A showing an embodiment in which a wave washer is used in the electric power steering apparatus of FIG.

  In the above embodiment, as shown in FIG. 4, an annular recess 9 d is provided on the end surface of the bearing fitting portion 9 c, which is the facing surface of the gear housing 9, which contacts the end surface of the motor side bearing 35 on the worm 31 side. A configuration in which 51 is fitted may be employed.

  As a result, when the motor housing 20 and the gear housing 9 are joined at the end surfaces 20b and 9b, the wave washer 51 eliminates a minute gap caused by a dimensional error between the worm 31 side end surface of the motor side bearing 35 and the bearing fitting portion 9c. Therefore, it is possible to prevent the play caused by the gap and the increase of gear hitting sound between the worm 31 and the worm wheel 29 due to the play.

  In addition, this invention is not necessarily limited to embodiment mentioned above, A various deformation | transformation is possible.

1 is a schematic configuration diagram illustrating an electric power steering apparatus according to an embodiment of the present invention. It is a motor axial direction fragmentary sectional view of the electric power steering device of the embodiment of the present invention. It is A partial enlarged view which shows embodiment which used the elastic member for the electric power steering apparatus of FIG. It is A partial enlarged view which shows embodiment using the wave washer for the electric power steering apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 3 Steering wheel 5 Steering shaft 7 Steering column 9 Gear housing 9b Flat end surface 19 Electric motor 19a Rotation output shaft 20 Motor housing 20
20a Tubular portion 20b Flat end face 21 Output shaft 29 Worm wheel 31 Worm 33 Bolt 35 Motor side bearing 37 Anti-motor side bearing 38 Nut 39, 41 Rubber damper 42 Preload mechanism 43 Bush 45 Preload pad 51 Wave washer

Claims (2)

An auxiliary power transmission mechanism including a reduction mechanism including an electric motor, a worm coupled to a rotation output shaft of the electric motor, and a worm wheel meshing with the worm wheel; and a motor housing for the electric motor and the reduction mechanism. In the electric power steering device configured to be separably coupled to the attached gear housing,
The worm is supported by the gear housing by two bearings so as to be finely movable in the axial direction and loaded with a preload toward the electric motor side,
Of the two bearings, a bearing closer to the electric motor is supported in the axial direction by the motor housing.   2. The electric power according to claim 1, wherein a ring-shaped elastic member is disposed on an opposing surface of the gear housing or the motor housing that contacts one side surface of the bearing on the electric motor side. Steering device.

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